1. Field of the Invention
The present invention relates to a wireless communication technology, and it particularly relates to a method for performing wireless communications with a terminal apparatus and a radio apparatus using the method.
2. Description of the Related Art
In wireless communications, it is generally desired that the limited frequency resources be used effectively. With the wide use of mobile phones and second-generation cordless telephone systems, such a demand is ever increasing. One of technologies that meet this request is a technique called OFDMA (Orthogonal Frequency Division Multiple Access). OFDMA is a technique where communications between a base station apparatus and a plurality of terminal apparatuses are performed at the same timing by allocating signals transmitted from the terminal apparatuses to mutually orthogonal frequency bands. In general, the OFDMA technique requires scheduling processing for allocating a plurality of terminal apparatuses to the respective frequency bands. In the conventional practice, a frequency band whose signal-to-noise ratio is high in a plurality of frequency bands is allocated to the terminal apparatuses. Also, terminal apparatuses whose received powers are close to one another are put together into a plurality of groups, and a frequency band is allocated to each of the plurality of groups.
In the OFDMA, demodulation processings such as FFT (Fast Fourier Transform) processing and AGC (Automatic Gain Control) processing are generally performed, at one time and all together, on signals composed of a plurality of subcarriers allocated to the same slot, at a receiving side. However, in a case where the same slot is allocated to different terminal apparatuses but a received power of one terminal apparatus is extremely lower than that of another terminal apparatus, the amplitude is adjusted based on a higher received power as a reference at the time of the demodulation processing such as the AGC processing. Thus a problem arises where the receiving performance deteriorates because the signal at the terminal of a lower received power cannot achieve a sufficient gain.